The present invention relates to a closure gate for a grain storage bin or silo which will automatically close upon the occurrence of an explosion or other critical condition in the area of a grain silo or grain handling area. In general, the closure gate of the present invention will remain closed unless a motive force is applied to move the gate into an open position. Upon cessation of the motive force, the gate will return to its closed position to cut off the flow of grain out of the bin or elevator silo.
In the grain storage industry, the storage handling and processing of large quantities of grains presents the existence of grain dust in and around the storage and processing facility. Grain dust is a substantial problem for grain handling facilities as the presence of grain dust constitutes a combustible material which can undergo ignition and burn at such a rate as to result in explosive combustion of the grain dust in the vicinity of the ignition point. In general, once the concentration of grain dust in an area reaches a critical level, it can be ignited in a number of different ways. The ignition sources identified as providing the highest probability of grain dust ignition are hot bearings, welding and cutting activities in the vicinity of the grain dust, conveyor belt slippage and misalignment, open flames, and foreign objects caught in machinery resulting in overheating. The ignition sources presenting a low probability of grain dust ignition are considered to be spontaneous combustion, static electricity, lightening and metal and stone sparks.
While the existence of grain dust cannot be eliminated in grain handling operations, the accumulation of grain dust can be prevented and procedures to control grain dust are a major aid in preventing explosions in grain handling facilities. To control grain dust, various "housekeeping" procedures are required within the grain handling areas. These housekeeping procedures consist of keeping grain transfer points and grain free fall areas dust tight or providing dust control for these areas. The ultimate object being to maintain any layer of grain dust in an area at less than one sixty fourth inches and an airborne concentration to less than 40 grams per cubic meter. If the amount of grain dust is kept below these parameters, it is generally believed that the concentration of grain dust is too low for dust ignition and explosive combustion to occur.
Though the above safety parameters have been known for some time, it nevertheless occurs from time-to-time that grain dust concentration becomes elevated and ignition of the grain dust results in explosive combustion in the grain storage facility. Such explosions generally cover a wide area of enclosed space, and the explosive force is devastating both in terms of human life and damage to the storage facility.
One of the causes of loss of life during a grain elevator explosion is from damage to the grain containment equipment resulting in the unrestrained flow of huge volumes of grain into the work areas of the grain storage facility. These "avalanches" of grain into the areas where humans are working can bury the workers under tons of grain. Such a disaster can cause rapid loss of life, and at a minimum, the obstruction of assistance reaching the workers affected by the explosion.
One manner in which this avalanche of grain occurs can be appreciated by reference to FIG. 2 showing a typical configuration of a grain storage facility. The grain storage silo 12 is situated above a tunnel area 18 containing grain-handling equipment and workers operating the grain equipment. Upon the occurrence of an explosion in tunnel 18, chute 20 can be torn from the ceiling of tunnel 18 allowing the grain in silo 12 to plunge into tunnel 18. It is in this circumstance that workers in tunnel 18 become buried in tons of grain.
Current grain handling structures are not equipped with any gates or closures which can close upon danger to chute 20 and prevent this catastrophic deluge of grain.